You are correct. The game automatically puts the associated heroes in their place. However, based on some talents that places troops in the rear line, you can use that to get around it. Even though Lunaris is on the rear line, 2 of the 5 have troops allocated to rear line. Which is why I now have steel wheels and he is on rear line. You have to look at the talents and skills not just what position they are in the lineup. All talents, skills, and crests add to the team makeup. That was just a beginners guide to help the beginner who does not know how to work talents and crests.